1. Field of the Invention
This invention relates to a locking type push-button switch and, more particularly, to a miniaturized locking type push-button switch which can be assembled easily.
2. Description of the Prior Art
There is a known locking mechanism, which has a heart-shaped groove and a single-acting pin, for a locking type push-button switch in which an operating unit can be locked in a fully pressed state. Such a locking type push-button switch consists of an operating unit, a spring urging the operating unit in a direction opposite to the direction in which the operating unit is normally pressed, a slide element holding a movable contact member therein and adapted to be slidingly moved on a substrate provided with fixed contact members, a single-acting pin, which consists of a wire rod bent at both end portions thereof, and which is adapted to be moved along a heart-shaped groove provided in the operating unit with one end of the single-acting pin slidably engaged with the heart-shaped groove, and an enclosure in which the above-mentioned elements are housed. The operating unit is locked in a fully pressed state by the movement of the single-acting pin along the heart-shaped groove.
FIGS. 1-8 illustrate a conventional push-button switch having an operating unit capable of being locked in a fully pressed state by the movement of such a single-acting pin along a heart-shaped groove. Among these drawings, FIGS. 1-4 are sectional views illustrating various stages of operation of the push-button switch arranged generally vertically, wherein FIG. 1 shows the push-button switch in a non-pressed state; FIG. 2 an operational stage in which the operating unit is in an intermediately pressed position; FIG. 3 an operational stage in which the operating unit is in a fully pressed position; and FIG. 4 an operational stage in which the operating unit is released from a pressing force after it has been pressed to a full extent. FIGS. 5-8 illustrate the relation between the heart-shaped groove and the single-acting pin with respect to various operational positions of the operating unit shown in FIGS. 1-4, wherein FIG. 5 shows the positional relation between the groove and pin with the operating unit in a non-pressed state; FIG. 6 the positional relation between the mentioned two with the operating unit in an intermediately pressed position; FIG. 7 the positional relation between the mentioned two with the operating unit in a fully pressed position; and FIG. 8 the positional relation between the mention two with the operating unit released from a pressing force after it has been pressed to a full extent.
When an operating unit 21 is in a non-pressed state or a preparative state, a cylindrical projection 25b" of a slide element 25 is in a lower end portion of a bore 21d provided in the operating unit 21 (refer to FIG. 1), and a lower bent portion 30b is of a single-acting pin 30 at a point 21e' of stability in a lower end portion of a heart-shaped groove 21e (refer to FIG. 5). In this preparative stage, fixed contact members 28', 28" are connected together electrically through a movable contact member 26.
When the operating unit 21 is then pressed at a head portion 21a thereof, a main portion 21c of the operating unit 21 is moved in the direction of the arrow A against the force of a spring 22 secured to a flange portion 21b thereof. Consequently, the cylindrical projection 25b" of the slide member 25 enters an inclined portion 21d' of the bore 21d formed in the main portion 21c of the operating unit 21, to be moved therein gradually in the upward direction as seen in FIGS. 1-3. As a result, a pressing force is applied clockwise to an arm portion 25b' of the slide element 25, so that a slide block 25a is oscillated clockwise about a shaft 25d. In accordance with the oscillatory movement of the slide block 25a, the movable contact member 26 loosely fitted in a recess 25c formed in the slide element begins to be moved slidingly to the left on an insulating board 27 (refer to FIG. 2). In the meantime, the lower bent portion 30b of the single-acting pin enters a right-hand portion of the heart-shaped groove 21e as the operating unit 21 is downwardly displaced, to be moved round counter-clockwise along the right-hand portion of the groove 21e in accordance with an amount of downward displacement of the operating unit (refer to FIG. 6).
When the operating unit 21 has been pressed to a full extent, the cylindrical projection 25b" reaches the uppermost portion of the bore 21d, and the slide block 25a is oscillated leftward to a full extent. Accordingly, the movable contact member 26 reaches an extreme left position, so that fixed contact members 28, 28' are connected together electrically via the movable contact member 26 to allow the electric circuit to be shifted (refer to FIG. 3). At this time, the lower bent portion 20b of the single-acting pin 30 reaches the upper end of the right-hand portion of the heart-shaped groove (refer to FIG. 7).
When the operating unit 21 is then released from the pressing force, a returning force is applied thereto via the spring 22 to allow the operating unit 21 to be upwardly moved. At this time, the lower bent portion 30b of the single-acting pin 30 falls in an upper end portion 21e' of the heart-shaped groove 21e. Consequently, the operating unit 21 cannot be moved upwardly any more and is locked in the position shown in FIGS. 4 and 8 as the operating unit 21 is urged upwardly by the spring 22. The electrical connection between the fixed contact members 28, 28' is thus maintained even after the operating unit 21 has been released from the pressing force.
When the operating unit 21 is in the position shown in FIGS. 4 and 8 is pressed again, the lower bent portion 30b of the single-acting pin 30 is moved to the upper end of a left-hand portion of the heart-shaped groove 21e, so that the operating unit 21 is unlocked. When the operating unit 21 is then released from the pressing force, it begins to be moved upwardly by the force of the spring 22. Also, the cylindrical projection 25b" is moved along the bore 21d in a direction opposite to the direction in which it was moved when the operating unit 21 was pressed for the first time, and the lower bent portion 30b of the single-acting pin 30 moves towards the lower point 21e' of stability along the left-hand portion of the heart-shaped groove 21e. When the operating unit has been returned to the original position, it is in such a state as shown in FIGS. 1 and 5, and the electrical connection between the fixed contact members is also returned to the original condition.
Referring to the drawings, reference numeral 23 denotes an enclosure, and 24 a plate spring adapted to urge the single-acting pin 30 in such a manner that the lower bent portion 30b of the single-acting pin 30 is engaged constantly with the heart-shaped groove 21e.
The above-described push-button switch permits the operating unit therein to be locked in a pressed state, and the dimensions thereof can be reduced to a great extent. However, it is necessary that the single-acting pin 30 and plate spring 24 be installed together in the enclosure 23. This makes it troublesome to assemble the push-button switch. Especially in the case of a miniaturized switch, the enclosure 23 is too small to allow a finger to be inserted thereinto, and it is very difficult to carry out an assembling work therefor. This could cause a badly assembled switch to be produced, and such a switch could be erroneously operated.
FIG. 9 is a perspective view of another type of conventional push-button switch, in which an operating unit is locked by the movement of a single-acting pin along a heart-shaped groove. In this drawing, the parts of the push-button switch which are equivalent to those of the push-button switch shown in FIG. 1, are designated by the same reference numerals, and detailed descriptions thereof will be omitted. The push-button switch shown in FIG. 9 is not provided with a spring (correspondingly to the spring 22 shown in FIG. 1) for use in returning the operating unit.
Referring to the drawing, reference numeral 31 denotes a single-acting pin formed by bending both end portions of a wire material in the same direction, and 32 a single-acting pin mounting member secured to an insulating board 27 at right angles thereto. The mounting member 32 is provided with a bore 32a for inserting one end portion 31a of the single-acting pin 31 thereinto, and a clearance hole 32b for inserting the other end portion 31b of the single-acting pin 31 thereinto. Thus, when the end portions 31a, 31b of the single-acting pin 31 are inserted into the bore 32a and clearance hole 32b, respectively, the single-acting pin 31 can be oscillated about the end portion 31a along the clearance hole 32b. The end portion 31b of the single-acting pin 31 is engaged via the clearance hole 32b with a heart-shaped groove formed in a main portion 21c of an operating unit 21. Reference numeral 33 denotes a plate spring attached to the single-acting pin mounting member 32. The plate spring 33 is adapted to urge constantly a projected portion 33a at the end portion 31b of the single-acting pin 31 so as to bring the end portion 31b into engagement with the heart-shaped groove (not shown).
The operation of this push-button switch is substantially the same as that of the push-button switch shown in FIGS. 1-8. The differences between the push-button switch shown in FIG. 9 and that shown in FIGS. 1-8 reside in only the arrangement and construction of the single-acting pin 31 and plate spring 33 in the former push-button switch. In the push-button switch shown in FIG. 9, the single-acting pin 31 and plate spring 33 are provided outside of an enclosure thereof unlike the single-acting pin and plate spring in the push-button switch shown in FIG. 1.
Consequently, no other parts can be provided within a space in which the single-acting pin 31 is moved in accordance with the displacement of the operating unit 21. This substantially hampers the miniaturization of the push-button switch. Moreover, such a single-acting pin easily contacts other parts to be often prevented from being operated properly.